ALISO VIEJO, Calif. (AP) -- Avanir Pharmaceuticals Inc. said Monday it is planning to test its drug Nuedexta as a treatment for agitation in Alzheimer's disease patients.

The company it will start a midstage trial of the drug by September. Nuedexta is a treatment for pseudobulbar affect, a condition that involves involuntary emotional outbursts like laughing or crying. It is associated with brain disease or injury. The FDA approved it in February 2011. Avanir is also studying the drug as a treatment for nerve pain in multiple sclerosis and diabetes.

Avanir said large numbers of Alzheimer's disease patients develop behavioral and psychiatric symptoms, including more than 80 percent of patients in nursing homes.

Shares of Avanir Pharmaceuticals gained 5 cents to $2.96 in morning trading.